1. Field of the Invention
The invention relates to methods and apparatus for monitoring digital systems and more particularly to digital monitors which detect malfunctions by comparing a selected number of digital bit patterns generated by the system being monitored to a sequence of stored digital numbers to determine that the correct bit patterns are being generated and that these bit patterns are in the correct sequence.
2. Description of the Prior Art
Prior art monitors for synchronous digital systems have typically utilized a memory of some type to store the bit patterns generated by the system being monitored. The monitor was synchronized with the system to be monitored such that the digital bit patterns stored in the memory were sequentially read and compared to the bit patterns generated by the monitored system. These bit patterns are identical if and only if the system being monitored is operating properly. One disadvantage of these systems from a standpoint of circuit complexity was the fact that each memory location required the storage of a number of bits equal to the number of bits in the pattern to be monitored even though the number of patterns to be monitored was relatively small.